The present invention relates to in-ear devices and more particularly to a method and an apparatus for determining in situ the acoustic seal provided by in-ear devices, such as hearing aid devices (HADs), ear protection devices (HPDs) and the like.
The noisy environment in our industrial society is a health hazard to numerous workers as well as to people engaged in recreational activities generating loud noises.
Users often wear earplugs when operating light machinery such as chainsaws or heavy machinery such as paper industry, printing industry, aircraft industry machines, when participating in sporting activities such as shooting, and when attending various spectator events such as automobile races, truck pulls, and rock concerts, and the like.
Prior art mentions xe2x80x9cuniversal fitxe2x80x9d type earplugs, these plugs are often termed xe2x80x9cuniversal fitxe2x80x9d because they are intended to adapt to the contours of any person""s ear canal to provide hearing protection. To install the xe2x80x9cuniversal fitxe2x80x9d earplug, the wearer must first compress and/or form the plug by kneading, wadding or rolling it up and then position the plug in his or her ear canal. In the case of the foam earplug, the plug must be inserted before it expands.
Those xe2x80x9cuniversal fitxe2x80x9d earplugs are difficult for many individuals to insert properly. If the plug is formed by the user incorrectly as it is inserted in the ear canal, wrinkles and voids may develop that allow sound leakage to the user""s eardrum, thereby reducing the protective effectiveness of the plugs to the wearer. Also, some of the plugs typically are larger than people may need because it has been designed to fit ear canals that are larger than average in hopes of accommodating a wide range of users. Finally, some users find xe2x80x9cuniversal fitxe2x80x9d earplugs to be uncomfortable and touching the foam earplug, to roll it, with dirty fingers can lead to infection of the external and middle ear.
Custom-molded earplugs can be an attractive alternative to xe2x80x9cuniversal fitxe2x80x9d earplugs and have advantages in their comfort, more reliable fit and lower long-term costs due to longer usable life. Also, custom-molded earplugs may offer certain hygiene advantages in dirty environments since the user does not have to compress or form them with their fingers prior to insertion.
Casting an earplug in situ using a self-curing resin is not an ideal method for creating a custom-molded earplug. A doctor or a trained technician will be required to make the mold since the mould""s manufacture requires a highly viscous resin or putty to be deposited deep in the patient""s ear. The objective when taking the ear mold is to obtain an impression, which follows all inner contours of the ear canal and which, has no voids or creases due to the trapped air pockets. Packing the resin in the ear canal to meet this objective can be very painful to the patient. After the resin is added to the ear, it may be necessary to manually apply some pressure from outside the ear to assure that the resin hardens within the canal. The patient must sit motionless, without jaw movement, for several minutes until the mold solidifies.
Besides severe pain being caused to many patients, casting an earplug in situ also suffers from the common problem of voids being formed therein which reduce the effectiveness of the final earplug produced.
Semi-custom-molded expandable earplug may also offer the same advantages. The person to be fitted with this earplug is first fitted with a pre-shaped earplug having the approximate shape of the ear canal of the individual. Preferably the pre-shaped device is made available in different basic sizes to obtain the closest size corresponding to the individual. The size chosen should allow a small gap to permit an optimum expansion accomplished with an injected settable compound material. It is very important in that case to be precise in the quantity of injected compound because a little excess can create an inflating pressure level that can be very painful to the patient and, at the same time, an earplug cannot provide an effective acoustic seal with less inflating pressure. It is very difficult or even impossible to attain that optimum expansion without determining in situ the acoustic seal provided by an earplug.
All the above specifically refer to earplugs but it is to be understood that it is similarly applicable to any in-ear device, the latter referring to either earplug device (or hearing protection device (HPD)) or hearing aid device (HAD) for which an attenuation level or an amplification performance level is seek respectively.
U.S. Pat. No. 5,757,930 issued to Seidmann on May 26, 1998 and U.S. Pat. No. 5,790,795 issued to Seidmann on Oct. 26, 1999 disclose an apparatus being adapted only for in-ear sound level measurement without any comparison with an environmental sound. U.S. Pat. No. 5,577,511 issued to Killion on Nov. 26, 1996 discloses the occluding object and method for measuring its occlusion from existing surrounding noise without wide band measurement from any control sound sources. This measuring device cannot effectively be used to determine an accurate sound level difference provided by the object.
Furthermore U.S. Pat. No. 5,044,373 issued to Northeved on Sep. 3, 1991 relates to the method and apparatus for measuring of sound pressure levels in the auditory canal of a person in connection with the fitting of said apparatus. Authors used the reference microphone located far from in-ear device and moreover, this apparatus may be inserted only besides traditional in-ear device. As a result, this invention misrepresented a real sound level difference provided by the in-ear device inserted into an ear canal of an individual and is especially unsuitable for measuring sound level difference provided by earplugs as opposed to amplification of hearing aid devices. According to this invention the best thing would be if its probe could be placed at a distance approx. 1 mm from the eardrum. However, it is difficult to do this while making sure that the probe does not touch the eardrum, the reason being that the length and shape of the auditory canal differ from person to person.
Additionally, there is no objective way of measuring an insertion loss (IL) value provided by an in-ear device. The IL estimation described in all standards (ANSI, ISO, CSA, etc.) is subjectively determined by the individual wearing the in-ear device, as better described herebelow.
An object of the present invention is to provide a method and an apparatus for determining in situ the acoustic seal provided by an in-ear device for either of a hearing protection/aid nature that obviates the above-mentioned disadvantages.
Another object of the present invention is to provide a method and an apparatus for determining in situ the acoustic seal provided by an in-ear device that ensures a perfect fit and a good acoustic seal of the device easily obtainable with a good comfort for the potential user.
A further object of the present invention is to provide a method and an apparatus for determining in situ the acoustic seal provided by an in-ear device that allows for an effective protection against noise in the case of hearing protectors and an elimination of the noise feedbacks in the case of hearing communication/aid devices.
Still another object of the present invention is to provide a method and an apparatus for determining in situ the acoustic seal provided by an in-ear device that allows for a monitoring of the ear canal occlusion during the settable compound injection session of expandable in-ear devices.
Still further object of the present invention is to provide a method and an apparatus for determining in situ the acoustic seal provided by an in-ear device that allows for an effective performance in the sound insulation, attenuation, communication, measurement and the like of in-ear devices.
Yet another object of the present invention is to provide a method and an apparatus for determining in situ the acoustic seal provided by an in-ear device that allows for an objective estimation of the insertion loss provided by in-ear devices, and an estimation value of any standard parameters that could be derived therefrom.
Other objects of the present invention will become apparent from a careful reading of the detailed description provided herein, with appropriate reference to the accompanying drawings.
According to an aspect of the present invention, there is provided an apparatus for determining in situ an acoustic seal provided by an in-ear device inserted into an ear canal of an individual, said in-ear device having a sound bore with an environment opening and an ear opening outside and inside said ear canal respectively, said environment opening being adapted to be removably engaged by a remote device such as a sound measurement device, a filter device, an amplifier device, a plug device and the like, said apparatus comprises a sound measurement device being said remote device and having a probe microphone and reference microphone isolated from each other and connected to a data processing unit having a control box and a reference sound source, both connected to a computer unit, said probe and reference microphones being adapted for measuring a sound pressure level inside said ear canal of said individual and a sound pressure level from said environment in close proximity of said in-ear device respectively, said sound pressure levels corresponding to a known noise signal created by said reference sound source at an inlet to the individual""s ear in a close proximity of said in-ear device, said data processing unit being adapted for recording and processing said sound pressure levels read by both said probe and reference microphones corresponding to said known noise signal to provide a corresponding calculated value of a sound level difference provided by said in-ear device.
Preferably, the in-ear device is expandable and further has an injection channel with an opened end outside said ear canal and a closed end inside said in-ear device adapted to receive a settable compound material allowing for said in-ear device to properly assume said ear canal of said individual, said apparatus being adapted for continuously monitoring said calculated value of said sound level difference while said compound material being simultaneously slowly injected into said expandable in-ear device via said injection channel, said data processing unit being adapted for advising to stop injecting said compound material into said expandable in-ear device upon obtaining a calculated value of a sound pressure level difference of said in-ear device achieving first occurring of being either substantially equal to a predetermined sound pressure level difference or a substantially time stable sound level difference conditions.
Preferably, either the predetermined sound pressure level difference or the time stable sound level difference is determined over a pre-selected frequency range.
Preferably, the computer unit includes a display member for displaying said calculated value of said sound level difference provided by respective of said in-ear devices.
Alternatively, the apparatus further comprises a second measurement device adapted to engage an environment opening of a sound bore of a second in-ear device inserted into a second ear canal of said individual, said second measurement device being simultaneously connected to said control box of said data processing unit for the same to simultaneously provide a second corresponding calculated value of a sound level difference provided by said second in-ear device.
Preferably, the control box is adapted for filtering and sequentially sending said sound pressure levels read by said probe and reference microphones of said in-ear device to said computer unit.
Preferably, the control box being adapted for filtering said sound pressure levels read by said probe and reference microphones of both of said in-ear devices and having a multiplexer for sequentially sending the same to said computer unit.
Alternatively, the in-ear device has a second sound bore with an environment opening and an ear opening outside and inside said ear canal respectively, said environment opening of said second sound bore being adapted to be removably engaged by a second remote device, said second remote device being either an amplifier device or filter device adapted for a pre-selected frequency window, said second remote device engaging said environment opening of said second sound bore during measuring said sound pressure levels by said probe and reference microphones.
Preferably, the computer unit contains pre-determined correction factors and a transfer coefficient, said apparatus determining an estimated insertion loss value provided by said in-ear device from said calculated value of said sound level difference and said pre-determined correction factors and transfer coefficient.
According to another aspect of the present invention, there is provided a method for determining in-situ the acoustic seal provided by an in-ear device inserted into an ear canal of an individual, said in-ear device having a sound bore with an environment opening and an ear opening outside and inside said ear canal respectively, said environment opening being adapted to be removably engaged by a remote device such as a sound measurement device, a filter device, an amplifier device, a plug device and the like, said method comprises the steps of:
a) providing said sound measurement device having a probe microphone and a reference microphone isolated from each other and a data processing unit having a control box and a reference sound source, both connected to a computer unit,
b) turning on said data processing unit;
c) connecting said measurement device to said data processing unit;
d) testing connection of said measurement device to said data processing unit by measuring a known noise signal from said reference sound source with said probe and reference microphones;
e) engaging said measurement device into said environment opening of said sound bore, said probe and reference microphones for measuring a sound pressure level inside said ear canal of said individual and a sound pressure level from said environment in close proximity of said in-ear device respectively;
f) sending a known noise signal from said reference sound source;
g) recording sound pressure levels read by both said probe and reference microphones corresponding to said known noise source signal;
h) processing said measured sound pressure levels;
i) obtaining a calculated value of a sound level difference provided by said in-ear device;
j) turning off said data processing unit;
k) disconnecting said measurement device from said data processing unit; and
l) disengaging said measurement device from said in-ear device.
Preferably, the method further comprises, after step b), the step of:
b1) performing calibration of said data processing unit to check proper connection of said control box to said computer unit.
Preferably, the in-ear device is expandable and further has an injection channel with an opened end outside said ear canal adapted to be removably engaged by a settable compound material injection device and a closed end inside said in-ear device adapted to receive said settable compound material allowing for said in-ear device to properly assume said ear canal of said individual, said method further comprises, after steps f) and i) respectively, the steps of:
f1) starting a slow injection of said compound material into said expandable in-ear device via said injection channel;
i1) repeating steps f) through i) to continuously monitor said calculated value of said sound level while simultaneously keeping on injecting said compound material;
i2) stopping said injection upon obtaining a calculated value of a sound pressure level difference of said in-ear device achieving first occurring of being either substantially equal to a predetermined sound pressure level difference or a substantially time stable sound level difference conditions.
Preferably, either said predetermined sound pressure level difference or said time stable sound level difference being determined over a pre-selected frequency range, said method further comprises, after step c), the step of:
c1) performing selection of said pre-selected frequency range for obtaining a corresponding calculated value of a sound pressure level difference.
Preferably, the computer unit including a display member, said method further comprises, between steps i) and i1), the step of:
ixe2x80x2) displaying said calculated value of said sound level difference provided by said in-ear device on said display member.
Preferably, the method further comprises, after step l), the step of:
I1) waiting for said settable compound material to properly set before performing any following step.
Alternatively, the in-ear device has a second sound bore with an environment opening and an ear opening outside and inside said ear canal respectively, said environment opening of said second sound bore being adapted to be removably engaged by a second remote device, said method further comprises, after step a), the step of:
a1) engaging said second remote device being either an amplifier device or a filter device adapted for a pre-selected frequency window to said environment opening of said second sound bore.
Alternatively, steps a) to i) are simultaneously performed for a second in-ear device inserted into a second ear canal of said individual and using a corresponding second sound measurement device adapted to engage an environment opening of a sound bore of said second in-ear device.
Preferably, the computer unit containing pre-determined correction factors and a transfer coefficient, said method further comprises, after step i), the step of:
ixe2x80x2) estimating an insertion loss value provided by said in-ear device from said calculated value of said sound level difference and said pre-determined correction factors and transfer coefficient.